Distance sensor device

ABSTRACT

A distance sensor device is described, in particular as a component of a parking aid or reversing aid for a motor vehicle, having one or more distance sensors (US, μW) and a distance sensor control device (US-SG) for the purpose of activating the distance sensor or sensors (US, μW) via a respective signal line using an activation pulse that is preferably quasi-digital and time-analog. At least one of the distance sensors (US, μW) has two different modes of operation. It is possible to perform switchover between the modes of operation by varying the duration and/or amplitude of the activation from the distance sensor control device (US-SG).

BACKGROUND INFORMATION

[0001] The present invention relates to a distance sensor device, in particular as a component of a parking aid or reversing aid for a motor vehicle, having one or more distance sensors and a distance sensor control device for activating the distance sensor or sensors by way of a respective signal line by means of an activation pulse that is preferably quasi-digital and time-analog.

[0002] Although it may be used with any distance sensor devices, such as distance sensor devices for ships, airplanes, etc., for example, the present invention and the problems upon which it is based shall be explained with reference to a distance sensor device as a component of a parking aid or reversing aid for a motor vehicle.

[0003] Parking and reversing aids are generally known as accessories for motor vehicles. These products include a number of up to ten ultrasonic sensors, a control device assigned thereto, and one or more acoustic or optoacoustic warning elements for the driver.

[0004]FIG. 5 illustrates a known ultrasonic distance sensor device for a reversing aid having four ultrasonic sensors US and a control device US-SG. Four signal lines as well as a power supply line and a ground line run from control device US-SG to a distributor V. From distributor V, one signal line as well as the power supply line and ground line run to each ultrasonic sensor US.

[0005] The activation of ultrasonic sensors US by way of the respective signal line occurs by way of a respective bidirectional open collector interface. Regarding the amplitude in question, the transmission occurs in a quasi-digital, but time-analog manner.

[0006]FIG. 6 shows an activation pulse produced internally in the control device for an ultrasonic sensor US of the known ultrasonic distance sensor device according to FIG. 5. Time t is plotted on the x axis and voltage amplitude U is plotted on the y axis.

[0007] The duration of this activation pulse, which activates the measuring procedure in ultrasonic sensor US, is t₁-t₀ (typically 300 μs). Thus, at the beginning of time t₀, ultrasonic sensor US begins to transmit its ultrasonic pulse.

[0008]FIG. 7 shows the signal response produced internally in ultrasonic sensor US for an ultrasonic sensor US of the known ultrasonic distance sensor device according to FIG. 5. Time t is plotted on the x axis and voltage amplitude U is plotted on the y axis.

[0009] A comparator, which is not shown, inspects the signal voltage of the ultrasonic transducer for a sufficiently high received amplitude, and the voltage is only assessed as the detection of an object above a certain minimum amplitude, in order to eliminate sound effects or interference effects.

[0010] The time interval between t₂ and t₃ shows the mechanical vibration of the sensor membrane as a result of the activation. The time between t₄ and t₅ has the detected ultrasonic energy that has been reflected by an object.

[0011]FIG. 8 shows the signals on the data line between control device US-SG and ultrasonic sensor US as a whole for the known ultrasonic distance sensor device according to FIG. 5. Time t is plotted on the x axis and voltage amplitude U is plotted on the y axis.

[0012] The time difference between t₀ and t₄ represents distance s between the reflecting object and ultrasonic sensor US that is calculated in control device US-SG. The following formulas shall apply:

s=c _(s) *t _(e)/2  (1)

[0013] and

t _(e) =t ₄ −t ₀  (2)

[0014] where c_(s) is the speed of sound in air.

[0015] Unfortunately, the measuring range of the ultrasonic sensors currently available on the market is limited to approximately 2 m.

[0016] Therefore, the problems underlying the present invention generally involve the object of creating a more flexible distance sensor device.

ADVANTAGES OF THE INVENTION

[0017] Compared to the known methods of attaining the object, the distance sensor device according to the present invention having the features of claim 1 has the advantage that it creates a distance sensor device that is compatible with the known ultrasonic sensor in its function and interface and creates the corresponding request-specific function control for an extended functionality by way of the transmitting/receiving line using the control device.

[0018] The similarity of function and interface of the microwave sensor to those of the known ultrasonic sensors has the advantage that the control device and the software may be used in the same manner with microwave sensors for its current functionality.

[0019] Other advantages are the possibility of mixing sensors having various physical properties or sensor principles and the possible structural similarity of the microwave sensor for various applications having different requirements regarding their numbers.

[0020] Using a control device, it is possible to change the measuring range and type of measurement for the requirements of different functionalities.

[0021] It is possible to perform a filtering of the measurement values using a microcontroller in the sensor, as well as a self-diagnosis of the control device and a remote diagnosis of the sensors.

[0022] The idea underlying the present invention is that at least one of the distance sensors has two different modes of operation and it is possible to switch between modes of operation by varying the duration and/or amplitude of the activation pulse of the distance sensor control device.

[0023] Advantageous refinements of and improvements on the distance sensor device disclosed in claim 1 may be found in the subclaims.

[0024] According to a preferred development, the distance sensors have several ultrasonic sensors and several microwave sensors, with the ultrasonic sensors preferably having one mode of operation and the microwave sensors preferably having several modes of operation. This corresponds to an extension of the known ultrasonic sensor device to microwave sensors, the latter being particularly suitable for switching between modes. Thus, a microwave sensor may therefore be implemented with a functionally compatible ultrasonic sensor interface and the ability to switch for various requirements. In this manner, it is possible for the requirements for, e.g., faster measurement cycles, greater ranges, monitoring of a distance section, calculation of the relative speed, data transmission, or strong EMC irradiation (EMC=electromagnetic compatibility) to be switched via the control device. The interface for emulating an ultrasonic sensor is then able to remain unchanged for the purposes of hardware.

[0025] According to another preferred refinement, a bidirectional open collector interface is provided between the distance sensor control device and the respective distance sensor. This interface is appropriate, durable, and known by the ultrasonic sensor control devices.

[0026] According to another preferred refinement, the various modes of operation include measuring range modes and/or signal transmission modes and/or test modes and/or service modes for the purpose of adjusting/calibrating the sensor.

[0027] According to another preferred refinement, the modes of operation include a digital signal transmission mode. In this manner, a switching of the time-analog, preferably quasi-digital interface into a bidirectional, digital interface with a fixed data format and established protocol may be implemented by means of an activation pulse from the control device. The design of a data transmission interface with lower transmission rates having the sensor is particularly advantageous.

[0028] According to another preferred development, the distance sensor control device is a common control device for all distance sensors that is connected to each distance sensor by way of a single signal line. Thus, the known ultrasonic sensor control device may be used for the functionality that has been extended according to the present invention.

DRAWINGS

[0029] Exemplary embodiments of the invention are shown in the drawing and explained in greater detail in the description that follows.

[0030]FIG. 1 shows a first embodiment of the distance sensor device according to the present invention using microwave sensors having the related art ultrasonic sensor device for parking aid and reversing aid applications;

[0031]FIG. 2 shows activation pulses generated internally in the control device for a microwave sensor for the distance sensor device according to FIG. 1;

[0032]FIG. 3 shows a second embodiment of the distance sensor device according to the present invention using microwave and ultrasonic sensors with the related art ultrasonic sensor device for parking aid and reversing aid applications in a mixed sensor setup;

[0033]FIG. 4 shows activation pulses generated internally in the control device for a microwave sensor for the distance sensor device according to FIG. 3;

[0034]FIG. 5 shows a known ultrasonic distance sensor device for a reversing aid having four ultrasonic sensors and one control device;

[0035]FIG. 6 shows an activation pulse generated internally in the control device for an ultrasonic sensor for the known ultrasonic distance sensor device according to FIG. 5;

[0036]FIG. 7 shows the signal response generated internally in ultrasonic sensor US for an ultrasonic sensor US of the known ultrasonic distance sensor device according to FIG. 5; and

[0037]FIG. 8 shows the signals on the data line between the control device and the ultrasonic sensor as a whole for the known ultrasonic distance sensor device according to FIG. 5.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0038] In the figures, the same reference characters describe the same elements or elements having the same function.

[0039]FIG. 1 shows a first embodiment of the distance sensor device according to the present invention using four microwave sensors μW with the related art ultrasonic sensor control device US-SG for parking aid and reversing aid applications.

[0040] From control device US-SG, four signal lines as well as a power supply line and a ground line run to distributor V. From distributor V, a signal line as well as the power supply line and the ground line run to each microwave sensor μW.

[0041] Each microwave sensor μW is activated via the respective signal lines using a bidirectional single-core open collector line. Regarding the amplitude in question, the transmission takes place in a quasi-digital, but time-analog manner.

[0042] A sequence control system built into each microwave sensor μW or the microcontroller located in each microwave sensor μW monitors the activation pulse of the request emitted by control device US-SG on the sending/receiving line and the signal line. Such a request may also be a request for calibration, display of the parameters that have been set, or for a reset.

[0043] If it has the form and duration of the activation pulse of a control device for ultrasonic sensors, it emulates the interface for ultrasonic sensors. The sensor begins the distance measurement and simulates the typical post-pulse oscillation of the ultrasonic sensor on the sending/receiving line. If an object is in the measurement range, time t₄ is calculated using the measured distance and the condition t₀=0=beginning of the measurement request according to the above formulas (1) and (2). At time t₄, the sending/receiving line is switched by the sensor to low, i.e., to the detection of an obstacle for a previously determined duration that allows for a secure detection of the confirmation signal by the ultrasonic sensor device. If several obstacles are detected in the detection range at various distances, the distance calculation and obstacle transmission are performed repeatedly according to the procedure described above.

[0044]FIG. 2 shows activation pulses generated internally in the control device for a microwave sensor for the distance sensor device according to FIG. 1.

[0045] The interface properties are now switched in order to support various functionalities of microwave sensors μW by limiting or varying the duration of the activation pulse.

[0046] Two basic mechanisms have emerged as being particularly useful in this connection.

[0047] The first basic mechanism is a change in the activation duration while maintaining the measured data transmission principle described above.

[0048] Here, the switching of microwave sensors μW to a measurement range of 0.2 m to 7 m with a measurement duration of 10 ms per measurement range cycle by means of an activation duration of 200 μs corresponding to (t₁′″−t₀′) in FIG. 2 or the switching to a measurement range of 0.2 m to 1.5 m with a measurement range cycle time of 2 ms at an activation duration of 100 μs corresponding to (t₁″−t₀′) in FIG. 2 shall be used as an example. In addition, (t₁″″−t₀′) in FIG. 2 describes a measurement cycle for ultrasonic simulation corresponding to 300 μs in the range of 0.2 to 2 m.

[0049] The second basic mechanism is switching the time-analog, quasi-digital interface into a bidirectional, digital interface having a fixed data format and established protocol by means of an activation pulse from control device US-SG. This activation pulse is shorter than the activation pulses used for the functional switching with the time-analog measurement data transmission principle. A duration of 52 μs corresponding to (t₁′−t₀′) in FIG. 2 has been found advantageous, which corresponds to a data transfer rate of 19200 BAUD.

[0050] In the established data format and protocol, a request is triggered by control device US-SG using a command word or a command word and data words, whereupon microwave sensor μW must respond with an acknowledgment or an acknowledgment with data words. As an exception, however, no acknowledgment is provided at reset.

[0051] After each cycle, (e.g., command word from the control device, acknowledgment with data words from the sensor, etc.) control device US-SG may switch microwave sensor μW to a different functionality by altering the activation duration.

[0052] The command words or the command words with data words from the control device may, for example, have the following contents:

[0053] sensor mode selection

[0054] measurement request

[0055] measurement type setting (distance using pulse, echo, operation, or speed by evaluating the Doppler signal)

[0056] setting of the measurement range

[0057] diagnosis request

[0058] time adjustment for triangulation and permanent reception

[0059] pure permanent reception

[0060] transmission of a pulse string

[0061] calibration

[0062] reset

[0063] The acknowledgment or the acknowledgment with data words from microwave sensor μW may have the following content, for example:

[0064] sensor identifier, number of data words, and distance to the nearest obstacles

[0065] sensor identifier, number of data words, distance to and speed of the nearest obstacles

[0066] sensor identifier and results of sensor diagnosis

[0067] sensor identifier and switching to receive mode

[0068] sensor identifier and data word of a pulse string

[0069]FIG. 3 shows a second embodiment of the distance sensor device according to the present invention using microwave and ultrasonic sensors with the related art ultrasonic sensor device for parking aid and reversing aid applications in a mixed sensor setup.

[0070] Here, different activation pulse lengths are interpreted differently by the different sensors.

[0071]FIG. 4 shows as an example activation pulses generated internally in the control device for a microwave sensor for the distance sensor device according to FIG. 3.

[0072] The duration of an activation pulse that triggers the measurement sequence in ultrasonic sensor US in a measurement range of 0.2 m to 2 m is t₁″−t₀′.

[0073] The duration of an activation pulse that triggers the measurement sequence in microwave sensor μW in a measurement range of 0.2 m to 1.5 m is (t₁*−t₀*).

[0074] Although the present invention has been described above with reference to preferred exemplary embodiments, it is not limited to such embodiments; rather, it may be modified in a multitude of ways.

[0075] If the sensor is always operated by the control device with its interface in the bidirectional digital mode, several sensors may be connected to one sending/receiving line. In this case, an explicit sensor identifier must always be included in the acknowledgment. In the case of a sensor <->control device point-to-point connection, a sensor identifier may be omitted.

[0076] A mixture of different modes for the microwave sensors (individually and according to requirements from the control device) is also conceivable.

[0077] The present invention is also not limited to ultrasonic and microwave sensors, but rather may be applied to any sensors. 

What is claimed is:
 1. A distance sensor device, in particular as a component of a parking aid or reversing aid for a motor vehicle, having: one or more distance sensors (US, μW); and a distance sensor control device (US, μS) for activating the distance sensor or sensors (US, μS) via a respective signal line using an activation pulse that is preferably quasi-digital and time-analog. wherein at least one of the distance sensors (US, μW) has two or more different modes of operation; and switchover between the modes of operation may be performed by the distance sensor control device (US-SG) by varying the duration and/or amplitude of the activation pulse.
 2. The distance sensor device according to claim 1, wherein the distance sensors (US, μW) have several ultrasonic sensors (US) and several microwave sensors (μW), the ultrasonic sensors (US) preferably having one mode of operation and the microwave sensors (μW) preferably having several modes of operation.
 3. The distance sensor device according to claim 1 or 2, wherein a bidirectional open collector interface is provided between the distance sensor control device (US-SG) and the respective distance sensor (US, μW).
 4. The distance sensor device according to one of the preceding claims, wherein the various modes of operation include: measurement range modes and/or signal transmission modes and/or test modes and/or service modes for the purpose of adjusting/calibrating the sensor.
 5. The distance sensor device according to claim 4, wherein the modes of operation include a digital signal transmission mode.
 6. The distance sensor device according to one of the preceding claims, wherein the distance sensor control device (US-SG) is a control device in common for all distance sensor devices (US, μW), which is connected to a respective distance sensor (US, μW) via a single signal line. 